#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=1e3+100;
typedef long long LL;
inline LL read(){LL x=0,f=1;char ch=getchar();	while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
char str[maxn];
bool vis[maxn];
int main(void){
   	cin.tie(0);std::ios::sync_with_stdio(false);
    LL t;cin>>t;
    while(t--){
        LL n,m;cin>>n>>m;
        cin>>(str+1);
        LL last=0;
        for(LL i=1;i<=n;i++){
            if(str[i]=='1') last++;
        }
        while(m--){
            LL sum=0;
            for(LL i=1;i<=n;i++){
                if(str[i]=='1') sum++;
                vis[i]=0;
            }
            for(LL i=1;i<=n;i++){
                if(str[i]=='1') vis[i]=1;
            }
            if(sum==n) break;
            for(LL i=1;i<=n;i++){
                if(str[i]=='0'){
                    LL pre=max(1LL,i-1);
                    LL suf=min(n,i+1);
                    if(str[i]=='0'&&vis[pre]&&!vis[suf]){
                        str[i]='1';
                    }
                    if(str[i]=='0'&&!vis[pre]&&vis[suf]){
                        str[i]='1';
                    }
                }
            }
            sum=0;
            for(LL i=1;i<=n;i++){
                if(str[i]=='1') sum++;
            }
            if(sum==last) break;
            last=sum;
        }
        for(LL i=1;i<=n;i++){
            cout<<str[i];
        }
        cout<<"\n";
    }

   	return 0;
}
